tentukan luas lingkaran yg diameternya : a) 42 dm b) 40 cm c) 90 m dibantu ya : D (pake cara)

d = 42 dm
r = 21 dm
L = 22/7 × 21²
L = 22/7 × 441
L = 1386 dm²

d = 40 cm
r = 20 cm
L = 3,14 × 20²
L = 3,14 × 400
L = 1256 cm²

d = 90 m
r = 45 m
L = 3,14 × 45²
L = 3,14 × 2025
L = 6358,5 m²

luas lingkaran :
= phi.r2
= 3,14 × 12 × 12
= 452,16cm2

= 3,14 × 20 × 20
= 1256cm2

= 3,14 × 45 × 45
= 6358,5cm2